seek cigs pathway thermocalc

1 | Program Name or Ancillary Text eere.energy.gov

Solar Energy Technologies Program Peer Review

Routes for Rapid Synthesis of CuGaxIn1-xSe2 Absorbers

Tim AndersonUniversity of FloridaChemical Engineering [email protected] 27, 2010

Program Team : PV

DICTRA• Atomic Mobilities

• Chemical Potentials

Seek CIGS Pathway

High-rate, high-quality,low temperature

Phase Diagrams

ThermodynamicProperties

CIGS FormationPathways & Kinetics

HT-XRD• Pathways• Rates• Mobilities

PathwayPrediction

ThermoCalc• Equilibria• G(T,P) database

2 | Solar Energy Technologies Program eere.energy.gov

2

• Project start date: 7/1/08• Project end date: 5/31/12 • Percent complete: 35%

Large Capitalization Cost►Need to increase throughput

- High-rate absorber synthesis- Lower temperature- Scale-up

• Total budget: $760,863 – DOE share: $599,556 – Contractor share: $161,911

• Funding received FY09: $48,684

• Funding received FY10: $79,941 (4/30/10)

Timeline

Budget

Barriers

Project lead: Tim AndersonCollaborators

Dr. Andrew Payzant, ORNLDr. Carelyn Campbell, NIST

Industry PartnersGlobal Solar NanoSolarISET Solyndra

Partners

Overview


Challenges and Barriers

Challenge: Lower Cost - $/Wp

Materials Costs (~50%)Processing CostsCapitalization largest cost

Increase Throughput high rate synthesislower temperaturescale-up

National Solar Technology Roadmap for CIGS PV calls for absorber synthesis rates of “30–40 μm/h and <1 μm CIGS absorber thickness” by 2015 or <2 min processing time

12

10

8

6

4

2

0M

eta

ls r

ate

s (Å

/s)

30

20

10

0

Se ra

te (Å

/s)

Se

In

GaCu

In

1st stage 2nd stage 3rd stage

-10 0 10 20 30 40 50 60

Run time (min)

Ga

400 °C

600 °COpenshutter


4

Relevance: Project and Phase 1 Objectives:

• Determine reaction pathway for synthesis of CuGaSe2, CuInSe2, and CuInxGa1-xSe2 from basic precursor structures using HT-XRDa) From basic precursor structuresb) From industry provided precursors

• Develop a thermodynamic model describing the contained Cu-In-Ga-Se ternary phase diagrams

Develop thermodynamic description of Cu-In-Se andCu-Ga-Se ternary phase diagrams

• Build diffusion mobility database to quantitatively predict synthesis ratesBuild diffusion mobility database for the Cu-In, Cu-Ga, and Ga-In binaries

• Transfer understanding to industry collaborators– Effect of annealing on grain size and texture and Ga distribution– Assess the feasibility of sub-2 min reaction time for CIGS synthesis– Support process scalinga) Effect of annealing on grain sizeb) Assess feasibility of <2 min reaction time for absorber synthesis

Phase 1

Phase 1

Phase 1

Phase 1


X-raytube

PSD

Chamber

In Out(He)

Capton/Be window

CW inout

Sampleholder

Panalytical Philips X’pert System

SurroundingHeater

High Temperature Materials Laboratory (ORNL)

Precursorsample

Selenium powder

Graphite Dome

Scintag-HTXRD also available

Approach to Pathway Analysis


Progress: HT-XRD StudiesBinary Precursors

In2Se3 (slow)

CuSe2/CuSe/Cu2-xSe(fast)

Cu7Se4/CuSe/Cu2-xSe(slow)

In4Se3/In2Se3(slow)

Ga2Se3 (fast)

GaSe (fast)


7

Approach to Developing Phase Diagrams

Data

Thermochemical& Equilibrium

Structure

• Literature• Measurements -EMF• First Principles• Estimation

Critical evaluation,Model selection &

Assessment

Bulk & Point Defects

Cu-Ga-In-Se System 4 unary sub-systems 6 binary sub-systems 4 ternary sub-systems

EquilibriumPhase

Diagrams

ThermoCalc(database)


Phase ModelLiquid (Cu+1)p (Se-2,Va-q,Se)q

Cu-rich fcc (Cu,Se) (Va)

α, β-Cu2-xSe (Cu,Va)1 (Cu)1 (Se)1

α, β, γ-CuSe (Cu)0.5 (Se)0.5

CuSe2 (Cu)0.33 (Se)0.67

Cu3Se2 (Cu)0.6 (Se)0.4

Chemicalpotentialof Se

Sublattice model

Progress: Cu-Ga-Se Phase DiagramCu-Se Binary System Assessment


Progress: Cu-Ga-Se Phase DiagramGa-Se Binary System Assessment

Phase Model Phase ModelLiquid (Ga+3)p (Se-2,Va-q,Se)q β-Ga2Se3 (Ga)2 (Se)3

α-Ga2Se3 (Ga,Va)2 (Se,Va)3 GaSe (Ga)1 (Se)1


Ga-In Cu-In Cu-Ga Nearly Degenerate

Eutectic Small solubility of

Ga in BCT(In)

Structural Similarity

Cubic Cu (-A1) type

Cubic InMn3 (-D83) type

β :

γ :

Progress: Cu-Ga-Se Phase DiagramMetal Binary Systems Assessment


11

Progress: Pseudobinary Systems Assessment

Mole % Ga2Se3 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Tem

pera

ture

K

1150

1200

1250

1300

1350

1400

1450

Palatnik&Belova 1966Jitsukawa 1998

Cu2Se Ga2Se3

β + δ

L1 + γ

ε δ

γ

γ + L2δ + L2

ε + L2

β−C

uGaS

e 2

γ +

δβ + γ

Cu 2

Se(

ss)

Cu2Se(ss)+β−CuGaSe2

L1+β−CuGaSe2

L1L2

xGa2Se3

0.0 0.2 0.4 0.6 0.8 1.0

Tem

pera

ture

K

1150

1200

1250

1300

1350

1400

1450Mikkelsen 1981CoolingCoolingHeatingHeating

Ga2Se3Cu2Se

Cu 2

Se(s

s)

Cha

lcop

yrite

(ss)

Zincblende(ss)

L

Cu2Se(ss) +Chalcopyrite

L+Chalcopyrite

L1+Zb Zb+L2

Ch+Zb

L1L2

CGS System• Most data – pseudobinary equil.• ΔGf CuGaSe2 measured• Conflicting phase diagrams• Need few definitive experiments

CuInSe2 CuGaSe2

CGS Pseudobinary Diagram CGS Pseudobinary Diagram

CIS Pseudobinary Diagram CIS-CGS Pseudobinary Diagram


12

Approach to Development of Diffusion Mobility Database

DATA

Experiments Theory

• Literature• Measurements Tracer, Intrinsic,Interdiffusion

Critical Evaluation and Parameter

Estimation for D

Reaction PathwayPrediction

Diffusion Mobility

Database

Diffusion CoefficientProduct of thermodynamic (∂µ/ ∂c) and kinetic (M) factors

D= M ⋅ ∂µ/ ∂c M=Mb+ exp (Mq/RT)

• First Principles• Estimation

Thermodynamic Database


13

Diffusion Mobility Accomplishments

10-12

10-11

10-10

0.22 0.225 0.23 0.235 0.24 0.245 0.25CuI

nSe 2 In

terd

iffus

ion

Coe

ffici

ent (

m2/

s)

Mole Fraction Cu

873 K

773 K 673 K

573 K

473 K

373 K

Predicted Interdiffusion in CuInSe2

10-25

10-23

10-21

10-19

10-17

10-15

10-13

10-11

1 1.5 2 2.5 3 3.5

Inte

rdiff

usio

n (m

2 /s)

1/T x 1000 (K)

1000 667 400500 333 286

Temperature (K)

Cu7In

3

CuIn-ηIn

2Se

3

Cu2Se

CuSe

CuGa2

Cu9Ga

4

Cu-InSolder Cu

t > 0 sCu11In9

0

10

20

30

40

50

60

70

0 5 10 15 20 25 30 35

In/CuCu-98.5In/CuCu-97In/CuCu97In/Cu calculatedCuIn/Cu calculated

Thic

knes

s of

Cu 11

In9 (m

icro

ns)

Time (hours)

►Diffusion mobilities assessed using

experimental data and estimates for

Cu-In, Cu-Ga, Cu-Se and In-Se systems

►Diffusion models used to treatbinary and ternary intermetallicsphases have been tested

►Diffusion data for Cu(In,Ga)Se2system reviewed

There is sufficient experimental data to model composition of the dependence of diffusion mobilities


Approach to Development of Diffusion Mobility Database

Approaches to High Rate Synthesis Pathway

RATEDecrease diffusion distanceFavor precursors/intermediate phases

with high species diffusivityAvoid those with low diffusivity

QUALITYControl nucleation, defect chemistry,grain growth, composition profile

Avrami model

lnk (s-1)

1000/T(K)

(1)

(6)

(3)

(4)

(5)

[441 °C] [203 °C]Precursors

Activation energy (kJ/mol)

Avrami Parabolic

1 InSe/CuSe 66 65

2 CuSe/In2Se3 N/A 162 (±5)

3 Cu-In + Se(vapor) 124 (±19) 100 (±14)

4 GaSe/CuSe 118 (±22) 107 (±15)

5 Cu-Ga + Se(vapor) 108 N/A

6 Cu/In/Ga + Se(vapor) 144 N/A

• Significant differences in rate• Co-evaporation is high rate


652.2Κ605.8Κ

UF11-2 (Cu/In= 1.260)

Before After

Approaches to High Rate Synthesis Pathway: CIS/CuSex Nanoparticles

Use eutectic valley orperitectic reactions to

liquid phase assist growth


Temperature Ramp Annealwith Se Overpressure

220

260

Tm of Se

2θ

330380

CuSe2CuSe2 Se

CuSe2 CuSe + L CuSe β-Cu2-x Se + L

27

100

60027

CIS(Cubic)

• Ramp anneal shows initial cubic CIS phase and CuSe2• Tetragonal CIS forms at 260 °C• Peritectic reactions occur consistent with the phase diagram


17

Collaborations

Industry PartnersGlobal SolarInternational Solar Electric Technology (ISET)NanoSolarSolyndra

Perform studies on industry provided samples to address their absorber synthesis processes. Share results of our research.

CollaborationsDr. Andrew Payzant, ORNL, Senior Member of R&D Staff

Collaborator in HT-XRD studies; leader of Diffraction User Center (DUC) in High Temperature Materials Laboratory-UF team DUC user.

Dr. Carelyn Campbell, NIST, Member of Staff, Metallurgy DivisionLeads effort to generate diffusion mobility database. Member of Thermodynamics and Kinetics Group, NIST supported.

Dr. Jianyun Shen, General Res. Inst. for Non-ferrous Metals of BeijingCollaborator in phase diagram assessments; annually visits lab (~3 mo).

Dr. Chinho Park, Yeungnam University, S. KoreaCollaborator in nanoparticle synthesis; sabbatical at UF


Graduate Students

Barrett Hicks(B.S. Auburn, 2007)

Chris Muzzillo (B.S. Purdue, 2008)

Ranga Krishnan(M.S. U. Toledo, 2007)


First Year Milestones

Milestones Met Pathways and rate constants for the base M-Se systems

indentified Cu2Se-Ga2Se3 pseudobinary phase diagram assessed Presence/absence of grain growth established

CRITICAL MILESTONE Evidence for 2 minute maximum absorber synthesis

time provided


Budget Status and Potential for Expansion

• Total 3-year Budget: $760,863.00 (DOE: $599,556, Cost share: $161,911)– Spending rate was initially low (delay in start date, recruiting

students). No-cost requested (additional industry collaboration, redesign of Se chamber).

• Additional funding – Hire post doc to focus on industry interaction (modeling, HT-XRD

and characterization)– Pursue Cu2ZnSnS4 pathway analysis (recent announcement of

9.6% cell)


FY 2011Plans

CuxSeInxSey

Mo/Glass

CuxSeCIGS

Mo/Glass

• HT-XRD experiments and data analysis of precursors • Explore bilayer precursor structures. Combinations of Cu2Se, CuSe, and CuSe2 with InSe, In2Se3, and In4Se3 will be examined.

• Industry provided base precursors: High rate precursors• Continue to work with industry to understand their process leading to increase throughput

• Development of diffusion mobility database• Assess mobility of the binary selenides using HT-XRD and other data• Complete assessment of Cu-In-Se system and evaluation of ternary reactions• Simulate observed pathways of CuInSe2 formation to verify the ternary diffusion

mobility database.

• HT-XRD experiments and data analysis of grain growth• Study the role of excess Cu on grain growth as function of Ga composition

• Assessment of available data and prediction of the metal Cu-Ga-In ternary phase diagram

• Binaries completed; equilibration studies of selected ternary compositions

Experimental results onCu-Ga-In ternary at 350°C


22

• Pathways <2 min reaction time for absorber synthesis identified– Low temperature route to grain growth of CIS nanoparticles using peritectic decomposition of

CuSe2 and CuSe. Novel CIS nanoparticle synthesis process also developed. Disclosure filed and cells being fabricated.

– Rate data for bi-layer and co-deposited precursors promising.

• Milestones Met – building CIGS foundational understanding– Reaction pathways for absorber synthesis using HT-XRD

• Completed HT-XRD studies of metal-Se bilayer and co-deposited films. Ga-based reactions are much faster than In-based ones, now working on binary layers and Mo-Se interaction.

– Phase Diagrams and Thermochemistry• Completed assessment of the 6 binary phase diagrams with common solution model (sub-lattice).• Initial assessment of CGS diagram.• Pseudo binary CIS-CGS phase diagram assessed and optimized.

– Diffusion mobility database for CIGS • Diffusion mobilities assessed for Cu-In, Cu-Ga, Cu-Se and In-Se • Tested diffusion models used to treat the binary and ternary intermetallics

• Worked with industry to understand their absorber synthesis process

• Highly leveraged program– Working with 4 companies, collaborators at 2 national labs, and 2 international institutions

Summary


23

Supplemental Slides


Ga2Se3

Ga2Se3

Ga2Se3

Ga+Se

Glass

25°C60°C

Ga2Se3Formation

500°C25°C

Se

210°C

SeCrystallization

xSe ~ 0.86

xSe ~ 0.59

Ga+Se Precursor Annealing


Glass

Ga

Se

25°C60°C

GaSe(101)

GaSe(008)

GaSe(110)

Se xSe ~ 0.80

xSe ~ 0.56

210°C

SeCrystallization

GaSe Formation

500°C25°C

Se/Ga Precursor Annealing


600K

ChemicalPotential(kJ/mol)

-160

-120

-80

-40

0

-2000 0.2 0.4 0.6 0.8 1

x(Se)

Se

Ga

Ga-Se Phase Diagram

Ga-Se Phase Diagram

seek cigs pathway thermocalc

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